11-17-2008, 15:23
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#1
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Quiet Professional
Join Date: Nov 2008
Location: NW and OCONUS
Posts: 41
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Zero Range for a 10.5 inch upper
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I need the bullet data on the M855, with a 10.5in upper(Colt and Bushmaster), with a EOTECH on it. Trying to find out what the zero range needs to be.
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Guys, this is a short fuse request from a friend of mine in DSS. They normally zero for 100m.
18B's, let's see what you got.
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Swank is offline
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11-17-2008, 15:25
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#2
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Quiet Professional
Join Date: Jan 2004
Location: Free Pineland
Posts: 24,804
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Quote:
Originally Posted by Swank
Guys, this is a short fuse request from a friend of mine in DSS. They normally zero for 100m.
18B's, let's see what you got.
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I hate to sound like a smart ass, but it depends on how far they are expecting to engage targets.
TR
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The Reaper is offline
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11-17-2008, 15:32
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#3
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Quiet Professional
Join Date: Nov 2008
Location: NW and OCONUS
Posts: 41
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100m.
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Swank is offline
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11-17-2008, 15:45
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#4
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Area Commander
Join Date: Aug 2004
Location: Texas
Posts: 1,355
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I went through this exercise myself recently.
First off, it is hard to say precisely without knowing what weight bullets they will be launching, but I assume they will be using 75 or 77 gr. rounds. Using 75 gr. TAP, POI is within roughly 1.25" of POA all the way out to 150 yards using a 100 yard zero. However, drop is about 4" at 200 yards and about 14" at 300. I hope that helps.
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jatx is offline
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11-17-2008, 15:47
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#5
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Quiet Professional
Join Date: Feb 2004
Location: Ft Bragg
Posts: 139
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1. Shoot irons for a 25m-300m zero. Point of aim at 25m is point of impact at 25m and 300m
2. Mount red dot optic of choice.
3. Co-witness red dot to irons sights.
4. Confirm red dot zero using ammo.
5. Mount IR Laser sighting device (PAQ4, PEQ2, PEQ15).
6. Put on NVG, set red dot to NVG setting.
7. Co-Witness red dot with IR Laser at anywhere from 100-300m depending on range you have, 300 is most preferred (using NVG looking through sight).
8. Confirm IR Laser sighting device on paper if you feel it is necessary with the 25m target using ammo.
If you do this right and you don't shoot like a shotgun on crack, you can do this with about 20 rounds per man.
Biggest problems ever seen were operator headspace and timing, ensure all sights are tightened down (#1 problem!!), ensure you know what each click on whatever sight you are using will move that sight at 25m. Know that 1 moa at 25m is a 1/4 inch, therefore 1/2 moa adjustments on your sight will move the bullet 1/8 of an inch at 25m.
Shoot 3-5 round groups, I prefer 5, the Army says 3, I say FTA and do it the way I know works, but that's just me, the bigger the group, the better the shift. Measure from the center of the group for moving the impact.
10.5's that are brand new shoot rather well at the range on the first day, just be sure to confirm those zeros ever few ranges, the sights can get quirky after a couple thousand rounds through them, I have seen up to 4 or 5 moa shifts from one day to the next on them, it was usually an EO Techs Fault though, the irons held true for the most part.
HTH
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optactical is offline
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11-17-2008, 15:48
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#6
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Quiet Professional
Join Date: Jan 2004
Location: Free Pineland
Posts: 24,804
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Quote:
Originally Posted by Swank
100m.
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Then why not zero at 100m.? It is not like the shorties are going to be useful at extended ranges much beyond that.
If you zero at a shorter range, you will be low at 100, longer range and you will be high at 100.
The bullet flies in an arc, like a rainbow. The 1.4" of the sight plane above the bore on the M-16/AR-15 series weapons exacerbates this effect. It crosses the sight line twice on the way to the zero target, once on the way up and once on the way down. That is how a 25m. zero puts the bullet on the target at 300m, and can hit all of the targets on the qualification range from 25 to 300m.
For this application, unless they are shooting almost exclusively closer, or further, I would leave it at 100, and shoot the intermediate distances to determine the holdover (or under).
Just my .02, YMMV.
TR
__________________
"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat." - President Theodore Roosevelt, 1910
De Oppresso Liber 01/20/2025
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The Reaper is offline
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11-17-2008, 15:59
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#7
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Quiet Professional
Join Date: Feb 2004
Location: Ft Bragg
Posts: 139
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The problem with zeroing at 100m with this barrel and optic is your group is relatively large. I always liked 25m/300m for general applications since I know where a 25m zeroed barrel will hit at 10m, 15m etc for CQB. Also, like you stated it covers the spectrum from 0-300 if aiming center mass.
If he wants to have a 100m zero, have him shoot a 25m zero first, this will get him on target, then shoot a 100m target and adjust down and for windage as necessary.
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optactical is offline
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11-17-2008, 16:00
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#8
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Quiet Professional
Join Date: Nov 2008
Location: NW and OCONUS
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Yep, I agree with that. DoS range master doesn't and wants to zero closer. This basically is two BFOC'ers (I can't rember what that stands for, basically a DoS range guy) trying to decide whether to zero these guys with 10.5 inch barrels at 50 or 75. The sr guy is saying 50. Other guy says 75. And one lonely former bat boy SOTIC grad who just wants to shoot his gun.
Last edited by Swank; 11-17-2008 at 16:04.
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Swank is offline
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11-17-2008, 17:11
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#9
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Asset
Join Date: Oct 2008
Location: South Coast
Posts: 43
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I agree with Rreaper. Zero the gun for 100m and get dope for 150-300 (300 is optamistic for a 10.5"). Most guys I know (including myself) use the 100m Zero for their shorties. Just don't forget to aim a little high at cqb distances.
BTW what is everyones take on the 200m zero for M-4 length? I've been using it for several years now. I find it works great for 14.5" uppers.
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Lmmsoat is offline
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11-17-2008, 17:16
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#10
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Quiet Professional
Join Date: Nov 2008
Location: NW and OCONUS
Posts: 41
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It has been decided. Yea, and the thunder clapped and the clouds parted, and 50m was handed down from on high. And there was much rejoicing. And cake.
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Swank is offline
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11-17-2008, 20:22
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#11
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Quiet Professional
Join Date: Jun 2004
Location: Occupied Pineland
Posts: 4,701
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Just to add to the confusion: http://www.professionalsoldiers.com/...t=Battle+sight
This is a thread that explains all of the variables for BSZs. (Thought I remembered this conversation at some point in the distant past. Love that search button!  )
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Peregrino is offline
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11-17-2008, 20:30
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#12
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Quiet Professional
Join Date: Dec 2004
Location: Nashville
Posts: 956
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Agree with 100 meters.
if you zero at 100 meters then the following:
M-193 ball = 4 inch target area out to 150 meters.
M-855 ball =4.2 inch target area out to 150 meters.
Added Info:
also if you zero the M193 ball @ 250ms you have +9.9 inch at 200ms, -15.1 at 300.
and for the M855 ball with 300 meter zero, = a +12.6 inches @ 150+
I'd do the 100 meter zero
Blitz
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